Centrifugal pulverizer



Dec. 22, 1964 o. DAN'YLUKE 3,162,382

CENTRIFUGAL PULVERIZER Filed March 22, 1962 2 Sheets-Sheet 1 INVENTOR.

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BY @Jg @J A T TOHIYEY5.

Dec. 22, 1964 o. DANYLUKE CENTRIFUGAL PuLvERIzER 2 Sheets-Sheet 2 FiledMarch 22, 1962 e, m mm ,0% mi. @M WW f l .8.7 A W, d Jaa w 0U. w L a Hf5 M United States Patent @ffice 3,162,382 Patented Dee. Z2, 19643,162,382 A CENTRHFUGAL PULVEUZER "Ostap Danylulre, Newtown Square, Pa.,assigner to Bath Iron Works Corporation, Bath, Maine, a corporation ofMaine' Filed Mar.. 22, i962, Ser. No; 181,552 7 (lairns. (El. 241-53)This invention relates to apparatusl for pulverizing or reducing to `adesired particle size such materi-als as ore, rock, pigments, clay, andthe like.

The object of my present invention is to provide apparatus forpulverizing such materials to a selected controlled .size as determinedby adjustments readily made to the pulverizing apparatus.

According to my present invention, the size to which the particles of yaparticular material are pulverized or reduced is controlled by a numberof factors, including the following: (l) The Velocity of a stream of airor other gas which is forced up 4through the pulverizer, as by a blower;(2) the angular positions to which a plurality of adjustable classifyingvanes are set; (3) the vertical position to which an adjustableclassifying sleeve is set; and (4) the rotative speed of the impeller.

In the appara-tus of my present invention, the air stream forced upthrough the housing divides into two paths, one of which is upwardthrough vents in the floor of the bowl and thus upward through theinterior of the bowl. The bowl referred to is the rotating bowl againstthe sides of which the particles to be crushed are thrown centrifugallyby the rapidly rotating impeller mounted in the bowl. The other pathfollowed by the forced air stream is up along the exterior wall of thebowl and upward along the interior wall of the housing through a narrowannular opening between the inner Wall of the cylindrical housing andthe outer upper edge of the bowl. The latter path makes unnecessary theprovision of wall Scrapers. Both air-stream paths then join, and thecombined air streams pass as a unit up through the remainder of theapparatus and out the product collection or discharge duct. The velocityof the air stream, as indicated above, is one of the factors whichcontrols the size of the particles carried out Ithe discharge duct, thegreater the velocity, the larger the particle size for a given material.

The radial positions of the adjustable classification vanes control thediameter of a spiraling path followed by the air stream Ias it movesradially inward from over the upper edge of an upper fixedclassification cone toward the entrance of the coaxially disposeddischarge duct. The greater the departure of the classification vanesfrom a radial position, the larger the diameter of the spiral and thesmaller the size of the product delivered to the dischargeduct.

The adjustable classify-ing sleeve controls the verticall level of theentrance to the discharge duct, the lower the sleeve position, the morethe air stream is forced downward and the liner the product delivered tothe discharge duct.

The structure of the centrifugal pulverizer of my present invention, andthe manner in which it functions, will become clear from a considerationof the following detaileddes'cription of a preferred embodiment selectedfor illustration inthe drawing in which:

FIG. 1 is an elevational view, partly in section, of a centrifugalpulverizer in accordance with my invention;

FlG. 2 is a plan View, in section, alongr the line Il-II of FIG. 1;

FIG. 3 is a plan View, in section, along the line lll-lll of FIG. l; and

FIG. 4 is an elevational View, partly in section, show'- ing afmodiiiedimpeller and bowl.

In describing the preferred embodiment. of the invention illustrated inthe drawing, specific terminology has been resorted to for the sake ofclarity. However, it is not the intention to be limited to the specificterms so selected, and it is to be understood that each specific termincludes all technical equivalents which operate in a similar manner toaccomplish a similar purpose.

Referring now to- FIG. l, the centrifugal pulverizer there shown ishoused in a cylindrical housing 20 having thereon a cap or cover 2lhaving a central opening for receiving the product collection ordischarge duct 22 and' also the input or feed tube 23, the verticalportion of duct 22 and the tube 23 being concentric.

Housing 2i) is supplied with an interior iioor Z4 on which is mounted abearing housing 25 which supports for rotation an impeller drive shaft26 and a bowlV drive spindle 27 which occupy concentric positions on thevertical axis of the cylindrical housing. Shaft 26 and spindle Z7 areadapted to be driven independently, either in opposite directions or inthe same direction, but at different speeds. In the drawing, it islassumed that impeller 40- and bowl 32 are rotated in oppositedirections. In FIG. l, impeller shaft 26 is shown as driven by motor(not shown) through drive belts 28 and a sheave 29, while bowl spindleZ7 is shown as driven `by a motor (not shown) through a drive belt 30and a sheave 31. The bowl 32, which is `adapted to be drivenrotationally by bowl spindle 27, is shown to be comprised of threesections, a lower section 33, a middle section 34, and an upper section35. The lower section 33 of bowl 32 comprises a generally circular floorsupported by spindlek 27 and having a central opening through which theimpeller drive shaft 2e passes. ln `the floor, intermediate itsouterportion and the impeller drive shaft 26 is lan annular depression ortrough 36, the outer wall of which inclines outward upward. Betweenannular trough 35 and the central hole occupied by the impeller shaft26a plurality of vents or openings 37 are provided at spaced intervalsalong an annular path around the impeller drive shaft 26.

An impactor ring 34 forms the middle section of bowl 32. The innerwallof impactor ring 34 Vinclines outward upward in line with the outerinclined wall of trough 36' but has a depression therein forming theannular recess 38.

The upper section 35 of bowl 32- also inclines outwardl upward at anangle of inclination equal to that of the inner wall of impactor ring 34and that of the outer wallA of trough 36. Thus, the lower, middle andupper sections of the bowl 32, when secured together, form a bowlstructure whose wall surface rises at a xed angle of inclination fromthe iioor of the trough 36 to the bowls upperi edge, broken only by therecess 38 in the impactor ringl 34. This xed angle of inclination ispreferably 35 from the vertical, as will be-discussed.

Mounted within bowl 32 on impeller drive shaft 26 and adapted to bedriven rotationally thereby is an impeller 40 having a circular discfloor 41 and generally radial spaced-apart arcuate webs 42, which curvein the direction of rotation of impeller 40, as indicated by the arrowin FIG. 3.l These webs 42, which are best seen in FIG. 3, support anannular cover plate 43, leaving a central circular opening into whichthe dome-like cap 44 of the impeller shaft 26- protrudes, therebyforming an annular opening 46 through which the particles to be crushedpass.

The webs 42 divide the impeller into a plurality 0f) arcuate sectors theperipheral edges of which are open and through which the particles areejected by the centrifugal force of the rotating impeller. outer ends ofthe webs 42 are removable wear shoes 47. These shoes are located at thepoints of maximum wear. The curved inward portion of the arcuate webs 42is sub-v Secured to the' at equally spaced locations around theperiphery of the cylindrical housing. v These directional' vanes 51 arecurved or arcuate, the outward curve of thefvanes as seen in FIG. 2being clockwise, which is opposite to the counterclockwise direction ofrotation of bowl 32, as indicated in FIG. 2 by the arrow. j v As bestseen in FIG. l, the four spaced-apart directional vanes 51 support apair of coaxial stationary cones, an upper cone 57 and a lower cone 45.V,Lower cone 45 is secured to the lower inclined edge of vanes 51, as bywelding, with itsv lower circular edge just above the annularopening 46leading to the impeller 40. Upper'cone 57, which is shown bolted to theupperV inclined edge of directional vane 51, terminates at its lower endin a depending cylindrical portion 58, Vthe lower circular edge of whichis located above the annular opening 46 leadingl to the impeller 40, andalso above the lower circular edge of cone-45. A

Secured to the wall of housing 20 just above the place of attachment ofdirectional vanes 51 isa defiector ring 50 having an angledcross-sectional shape. In the crotch of the angle of ring 50 is weldedan annular bar or ring 53 and into bar 53 bolts 59 are threaded.

- Pivotally secured to cover 21 of housing 20 are a plurality ofclassification vanes 55 spaced apart along an annularrpath. In apreferred embodiment there are 18 such classification vanes. These vanes55 depend from the `cover 21 and occupy positions just above the Vupperedge of upper cone 57. The radial position of these vanes the axis ofthe cylindrical husing20, extending down into housing coaxially throughupper cone 57 tov a' point above the dome cap 44 and the annular opening46 to the impeller 40. f, j

Located at a level belowthek floor of-the bowl` 32 in the wall ofhousing 20 is an air input duct through which air is forced as by ablower not shown. Y

In operation, th'ey particles of material, `such as ore,

rock, pigment, clay, etc., which` are to be1 reduced to a.

motor (not shown) through drive belts 28, sheave 29 and'shaft 26, whilethe bowl 32 is shown as being driven by a motor (not shown) through adrive belt 30, sheave 31, and spindle 27. y

The positional arrangement of bowl 32 relative to impeller is such thatrecess 38 of impactor ring 34 is on a level .with the impeller. Thus,asthe impeller revolves at high speed, the particles thrown out aredirected towardy recess 38 and wouldv strike the wall of therecess wereit not for the fact that, in operation,;as already indicated,uthe recess38 itself is substantially filled with particles of material whichclingV thereto due to the cenktrifugal forces set up by the rotationofthe bowl. Theresize by the forceof impact of still othergparticlesthrown out lby the rapidly rotating impeller.'y The force of theLlater-arriving particles in combination with the centrifugal forces setup by the rotation of the rotating bowl 32 cause the smaller and lighterparticles to move upward on the 'i inclined wall of the upper portion 35of the bowl along a pathV which curves in the direction of rotation' ofbowl 32.y Included among the particles which are forced up- Ward aresome medium sized particles, represented in FIG. 1 by the relativelysmall circles. When the upwardly-climbing particles rise above. theupper edge of the bowl, they hit the arcuate directional vanes 51 andare re-directed inward toward cone along a curving path counterrto thatfollowed by the particles asy they climbed upward along the wall of thebowl. 7

The upward movement of particles along thewall of bowl 32 is aided by astream of air of controlled velocity which is injected into the housing20 through the air input duct 52 and which is forced upY through thevents or holes-37 in the'iioor of the bowl 32, as indicated in FIG.

1 by the dashed-line arrow r60.

In accordance with my present invention, a portion of the air which isforced into the housing 20 throughthe air input duct 52 passes upwardalong the outer surface ofthe Wall of bowl 32 and through the narrowannular opening 39 between the upper outer edge ofthe rotating bowl andthe inner-wall of the' housing, as indicated by thefdashed-line arrow61.

Above the upper-edge of the rotating bowl 32, the air from the two'paths 60'and 61 just described combinefto force the particles upward.Some are too heavy preselectedA desired size, are fed, as from a hopper,into v. i.

the vertically disposed feed tube 23, drop downV the feed tube 23, andare diverted by the dome-like cap 44 of the impeller shaft 26into theannular opening 46 leading -to the impeller A40. These particles,whichare represented in FIG. 1 by the relatively large circles, fallonto the floor of the rapidly rotating impeller 4lfand are thrown' outby centrifugalrforce toward the recess 38 in the impactor ring 34. Thespeed at which the thrown particles leave the impeller, is substantiallyequal tothe peripheral speedof the rotating impeller. In a typical case,impeller 40 may be rotatedat from 23-50 to 3600 r.p.m.

Assuming the,` machine .to have been in operation `for at least a shorttime, particles from previously thrown particles are already intherecess 38 of impactor ring 34. These particlescling to the recess38due to the centrifugal forcesestablished by the bowlfs rotation..v In atypical case, bowlV 32 maybe rotated'rat from 300 to to be carriedby'the air -stream and fall down into the fixed cone 45, as representedby the arrow 62. Others are carried upward but strike against theinwardly projecting undersurface of deflector ring 50, and are deflectedback into `the cone 45. Those particles which enter cone 45, for either`of the aforesaid two reasons, are returned through opening 46 Ito theimpeller and pass through another reducing action.

The lighterand. some of the intermediate sized particles,even thoughdeflected by ring 50, arel sufficiently llght to be carriedby the airstream upwardly along a generally Ispiraling path following the contourof the arcuate vaines 51. These particles are carried by the air streammward over the upper edge of the upper cone 57 and past the vanes 55,Vas represented by thev arrow 63 in FIG. 1. The particles are carriedslightly downwardly along a spiral path a'nd'thenl the lighter particlesare drawn upward through lthe vertically adjustable -sleeve 56 andoutward through the product collection or discharge condu1tr 22, asrepresented by'arrow 64. Some offthe heavier of the particles whichyreach the position represented by arrow 63 are unable` to be returnedupward by alsaasa for a given material, the particle size of the productdelivered by the apparatus is a function of a number of factors, one,the velocity of the air stream; two, the position of the classificationvanes (55); three, the position of the classification sleeve (56); andfour, the rotative speed of the impeller.

The classification role played by the air stream is believed to beapparent. The greater the velocity of the air Stream, the larger is theparticle size of the product delivered through the discharge conduit 22.The division of the air stream into two paths, one interior of thepulverizing bowl and the other exterior of the bowl, is advantageous inthat the exterior stream keeps the wall of the housing above the bowlfree and clear of particles which would otherwise tend to cling thereunder the force of the air stream which sweeps up through the interiorof the bowl toward the Wall of the housing, as indicated in FIG. l bythe arrow 66.

The classification vanes 55 control the path of the air stream as itmoves inward from over the upper edge of upper cone 57 toward the sleeve56 and discharge duct 22. Ordinarily, each of the (eighteen) vanes 55will be set at the same angular position relative to the radialposition. The greater the departure of the vanes 55 from the radialposition, the greater is the deliection of the air stream, and thelarger is the diameter of the spiral path into which the air stream isforced by the vanes within the cone 57. The larger the diameter of thespiral path, the greater the number of the heavier particles which arethrown against or near to the wall of the cone 57 and return downward tothe impeller and the fewer the number of particles which are borne bythe air stream up through the sleeve 56 and out the product collectionduct 22. If the classification vanes 55 are set on the radials, the airstream is not defiected at all into a spiraling path, and the greatestis the number of particles which are carrled out the discharge duct 22.In summary, the closer the classification vanes 55 are set to the radialposition, the eoarser is the product delivered by the pulverizingapparatus.

The vertical or elevational position of the adjustable sleeve 56 alsoplays a role in the classification process. The lower the position ofsleeve 56, the finer is the product delivered out the discharge conduit22. This results from the fact that the air path to the sleeve entrancefrom the upper edge of cone 57 involves a downward portion the depth ofwhich increases as the sleeve is lowered. In

FIG. l, sleeve 56 is shown in itsrlowermost position. Arrow 63 indicatesthe downward path of the air stream, which may be either a spiral pathor not, according to the position of the vanes 55, as previouslydescribed. The momentum of. the larger particles as they move downwardmakes it more difficult for the up-sweep of the air stream, when itoccurs, as indicated by arrow d4, to carry with it the larger particles,and these continue downward and are returned to the impeller.

The largest or coarsest particle size in the delivered product isdependent on air velocity, but the impeller speed has a decided effecton the number of smaller particles in the product. That is, the top sizeremains fairly constant (as controlled by air velocity) but as theimpeller speed increases, thepercentage of the larger particles isreduced, and as the impeller speed is decreased, the percentage ofcoarse material below top size increases.

In FIG. l, the restriction to the flow of the air stream up through theinterior of the pulverizing bowl 32 may, at first glance, seem to bemuch less than the restriction offered by the narrow annular opening 39through which passes the air stream which is exterior of the bowl. Ihave found, however, that the total air input at duct 52 divides aboutequally between the two paths. This is because the rapid rotation of theimpeller 40 sets up a high pressure area in front of the impactor ring34 into which the particles of material are thrown. This tends, ofcourse, to impede the iiow of the forced air therethrough.

The four arcuate vanes 51 serve the double purpose of supporting cones57 and 45 and of directing the larger particles of material back to theimpeller for further pulverizing. These four vanes 51, together with theair flow forced up through the narrow annular opening 39 makeunnecessary the provision of Scrapers to clear the housing wall and toreturn the larger particles to the impeller. The elimination of the needfor Scrapers is a decided advantage since such scrapers tend to wearfairly rapidly and to require replacement.

It will be seen that in my new pulverizer the particles of material arerecirculated until crushed to the size desired, as controlled by thecontrols described above.

It is important to the movement of particles up the wall of thepulversizing bowl 32 that the wall of the bowl have an inclination of 35relative to its vertical axis of rotation, i.e., 55 relative to thehorizontal axis. I have found that if the wall of the bowl be less steepthan 35 from the vertical axis, the particles 'of material will merelybuild up on the bowl wall until an angle of 35 (from the vertical axis)is reached before the particles will climb up and beyond the wall. Thus,if the bowl wall is less steep than 35 (from the vertical axis), theproduction action of the machine following start-up is slowed.

Trough 3o in the floor of the bowl 32 has two func' tions. When themachine is shut down, trough 36 tends to trap and collect the particleswhich were in recess 38 and on the wall of the bowl at the time ofshut-down. In the absence of trough 36, these particles tended to fallthrough the vents 37 and to drop to the floor of the machine,necessitating cleaning from time to time. With trough 36, the particleswhich are caught at time of shutdown are thrown upward by centrifugalforce when the machine is again started and brought up to speed.

The other function of trough 36 is to trap and catch the heavier of theinitially fed particles which, in the absence of trough 3d, tended todrop from the feed chute 23 through the vents 37 all the way down to thedoor of the machine.

In FIG. 4, I have illustrated a modification of the apparatus justdescribed. In this modification, the impeller le@ is a double-deck unit.Radial webs (corresponding to webs 42 in FIG. 3) support the upper deck.The impactor ring i3d is provided with two recesses, one opposite eachimpeller deck. In the arrangement shown in FIG. 4, particles returningto the impeller by way of the lower fixed cone are returned to the upperdeck, while particles fed to the impeller from the feed chute 123, or

returned to the impeller by way of the upper fixed cone` 157, arereturned to the lower deck. In other respects, the pulverizing machineof FIG. 4 is similar to that of FIGS. l-3, described above.

Incidentally, with respect to the curved impeller ribs or webs 42illustrated in FIG. 3, tests have shown that the particles of materialwill build up in the outer part of the curved portion of the web untilthe material forms an' angle of 39l relative to the radial from the tipof the web. This angle appears to be independent of impeller speed,material, and contour of web.

While the preferred embodiments of this invention have been described insome detail, it will be obvious to one skilled in the art that variousmodifications may be made without departing from the invention ashereinafter claimed.

Having described my invention, I claim:

l. A centrifugal pulverizer comprising: a cylindrical housing having acover; a bowl mounted for rotation in said housing, said bowl having aninclined wall having an annular inner recess, the upper edge of saidbowl forming with the inner wall of said housing a narrow annularopening, the fioor of said bowl having Vents therethrough; means forrotating said bowl; an impeller mounted for rotation within said bowlfor ejecting particles toward the recess in the wall of said bowl, saidimpeller having .a central opening through which particles to bepulverized may be dropped into said impeller; means forV rotating saidimpeller at a speed vsubstantially higher than the rotative speed ofsaid bowl; Va plurality of arcuate directional vanes generally radially'disposed and secured at `spaced-apart circumferential locations to thewall of said housing; a lower stationary cone secured to saiddirectional vanes Iand supported thereby in an axial position, the lowerportion of said cone extending down into saidbowl and terminating abovesaid central opening of said impeller; an upper stationary cone securedto said directional vanes and supported by `said vanes in an .axialposition `above said lower cone, the lowerportion of said upper conebeing cylindrical and extending down within said lower cone andterminating above lsaid irnpeller opening; a feed tube verticallydisposed on'the .axis of said housing and extending down through saidcover and down through said upper and lower cones'to a point above saidimpellerropening; a product collection conduit having a portionvertically disposed on the` axis of said housing and surrounding saidfeed tube concentrically at the cover of said housing; a plurality ofclassification vanes mounted below the cover of said housing atspaceddocations along anannular path, said classificationV vanesoccupying positions ad jacent the upper edge of said upper cone andbeing adapted to be adjusted from radial positions to positions formingan acute angle with the radial line; and external means for forcing airinto and upwardly through said housing and out said collection conduit,said housing and its fixtures providing two paths for said forced air,oneV` t upward through the vents in the oor of said bowl along the innerwall of said bowl and the other upward along the outsiderof said 'bowland'throngh the annular openingl ing upward along the outer wall of saidupper cone, Vin-` ward into said upper co-ne, then upward and outthrough said product collection conduit, the radial position of saidplurality of classication vanes controlling the path of the inward flowof air into said upper cone. 2. Apparatus as claimed inclairnlcharacterized in the` provision of a vertically adjustable 'sleeveadapted to extend downward from the housing-cover end of said collectionconduit', said sleeve'.beingadaptedV to provide a downward component tosaid inwardtlow of air into said upperl cone accordingV to the vertical4position Vof'said sleeve. l Y y Y 3. Apparatus as claimed in claimv 2characterized in that the wall of said'bowl is inclined at an angleV ofabout 35 from the vertical axis.

4. Apparatus as claimed in `claim 3 characterized in that the floor ofsaid .bowlis provided with an annular trough.` 1

' 5. Apparatus as claimed in claim 4 characterized'in 55 that saidimpeller has vcontiguous upper and' lower decks,

each having a central opening leading thereinto, the open- ,ing to theupper deck being larger.

` deck. 1

' 7. A centrifugal pulverizer comprising: a cylindrical housing having acover; a bowl mounted forY rotation in said housing, saidfbowl having aninclined wallthe upper edge ofv which formswith the inner wall of 'saidhousing a narrow annular opening, said ybowl wall having an annularinner` recess substantially below its uppergedge, the

tloor of said lbowl:havingvents therethrough; means for rotatingsaidbowl; an impeller Imounted' for rotation within said bowl forejecting particles toward the recess l in the inner wallof said bowl,said impeller having a central opening through which particles to bepulverized v may bedroppedinto said impeller; means for rotating saidimpeller at a speed substantially higher than ythe rotative speed ofsaid bowl; aplurality of arcuate directional. vanes generallyradiallydisposed Vandseoured at `spaced-apartv circumferentialy locations to thewall-of said housing;V a lower stationary cone vsupported in an ,axialposition above said impeller opening; an upper stationary conesupportedin an axial position above said lower cone; a feed tube verticallydisposed on the axisof said housing and extending down through saidcover and down through said upper and'lower cones to a point above saidirnpeller opening; a ,product collection conduit having a portionvvertically disposed and entering said housing rthrough 'the coverthereofra plurality of classilication vanes mounted along anannular pathand occupying positions adjacent the uppencdge Aof said upper cone andadapted to be adjusted from radial positions lto positions formingananglewith lthe radialline; and external means yfor lforcingfai'r,intoand upwardly through rsaid housing and out said collection conduiisaidhousing and-its lixtures providing two paths forsaidfforced air, oneupward through the vents in the floor ofsaid bowl along the 'inner Wallof saidvbowlandA ltheo-ther upward along the outside of' said bowl andthrough vthe annular opening between the upper edge of said bowl and theinner wall of said housing, said air paths then combining andpassing'lupward along the outer wallgof said upper conein jwardl intosaid upper cone, then upward and cnt through said Vproduct collection'conduit, -therradia'l position of said plurality of classification vanescontrolling the path of the inwardilow of airintosaid upper cone.;

' kReferences Cited in the le of this patent UNITED VSTATES PATENTS Y 11,148,159 France Mar. 31, 1959

1. A CENTRIFUGAL PULVERIZER COMPRISING: A CYLINDRICAL HOUSING HAVING ACOVER; A BOWL MOUNTED FOR ROTATION IN SAID HOUSING, SAID BOWL HAVING ANINCLINED WALL HAVING AN ANNULAR INNER RECESS, THE UPPER EDGE OF SAIDBOWL FORMING WITH THE INNER WALL OF SAID HOUSING A NARROW ANNULAROPENING, THE FLOOR OF SAID BOWL HAVING VENTS THERETHROUGH; MEANS FORROTATING SAID BOWL; AN IMPELLER MOUNTED FOR ROTATION WITHIN SAID BOWLFOR EJECTING PARTICLES TOWARD THE RECESS IN THE WALL OF SAID BOWL, SAIDIMPELLER HAVING A CENTRAL OPENING THROUGH WHICH PARTICLES TO BEPULVERIZED MAY BE DROPPED INTO SAID IMPELLER; MEANS FOR ROTATING SAIDIMPELLER AT A SPEED SUBSTANTIALLY HIGHER THAN THE ROTATIVE SPEED OF SAIDBOWL; A PLURALITY OF ARCUATE DIRECTIONAL VANES GENERALLY RADIALLYDISPOSED AND SECURED AT SPACED-APART CIRCUMFERENTIAL LOCATIONS TO THEWALL OF SAID HOUSING; A LOWER STATIONARY CONE SECURED TO SAIDDIRECTIONAL VANES AND SUPPORTED THEREBY IN AN AXIAL POSITION, THE LOWERPORTION OF SAID CONE EXTENDING DOWN INTO SAID BOWL AND TERMINATING ABOVESAID CENTRAL OPENING OF SAID IMPELLER; AN UPPER STATIONARY CONE SECUREDTO SAID DIRECTIONAL VANES AND SUPPORTED BY SAID VANES IN AN AXIALPOSITION ABOVE SAID LOWER CONE, THE LOWER PORTION OF SAID UPPER CONEBEING CYLINDRICAL AND EXTENDING DOWN WITHIN SAID LOWER CONE ANDTERMINATING ABOVE SAID IMPELLER OPENING; A FEED TUBE VERTICALLY DISPOSEDON THE AXIS OF SAID HOUSING AND EXTENDING DOWN THROUGH SAID COVER ANDDOWN THROUGH SAID UPPER AND LOWER CONES TO A POINT ABOVE SAID IMPELLEROPENING; A PRODUCT COLLECTION CONDUIT HAVING A PORTION VERTICALLYDISPOSED ON THE AXIS OF SAID HOUSING AND SURROUNDING SAID FEED TUBECONCENTRICALLY AT THE COVER OF SAID HOUSING; A PLURALITY OFCLASSIFICATION VANES MOUNTED BELOW THE COVER OF SAID HOUSING AT SPACEDLOCATIONS ALONG AN ANNULAR PATH, SAID CLASSFICATION VANES OCCUPYINGPOSITIONS ADJACENT THE UPPER EDGE OF SAID UPPER CONE AND BEING ADAPTEDTO BE ADJUSTED FROM RADIAL POSITIONS TO POSITIONS FORMING AN ACUTE ANGLEWITH THE RADIAL LINE; AND EXTERNAL MEANS FOR FORCING AIR INTO ANDUPWARDLY THROUGH SAID HOUSING AND OUT SAID COLLECTION CONDUIT, SAIDHOUSING AND ITS FIXTURES PROVIDING TWO PATHS FOR SAID FORCED AIR, ONEUPWARD THROUGH THE VENTS IN THE FLOOR OF SAID BOWL ALONG THE INNER WALLOF SAID BOWL AND THE OTHER UPWARD ALONG THE OUTSIDE OF SAID BOWL ANDTHROUGH THE ANNULAR OPENING BETWEEN THE UPPER EDGE OF SAID BOWL AND THEINNER WALL OF SAID HOUSING, SAID AIR PATHS THEN COMBINING AND PASSINGUPWARD ALONG THE OUTER WALL OF SAID UPPER CONE, INWARD INTO SAID UPPERCONE, THEN UPWARD AND OUT THROUGH SAID PRODUCT COLLECTION CONDUIT, THERADIAL POSITION OF SAID PLURALITY OF CLASSIFICATION VANES CONTROLLINGTHE PATH OF THE INWARD FLOW OF AIR INTO SAID UPPER CONE.